Corner Cube Prism (Retroreflector): Specs & Applications
A corner cube prism — also called a retroreflector or trihedral prism — has three mutually perpendicular reflecting surfaces meeting at a single point, like the inside corner of a cube. That geometry reflects any incoming beam straight back parallel to its original direction, no matter what angle it arrives at.
Key Specifications at a Glance
| Parameter | Typical Value |
|---|---|
| Substrate | N-BK7, UV fused silica |
| Aperture | 5 mm–50 mm |
| Beam deviation | 180°, largely independent of incidence angle |
| Surface flatness | λ/4–λ/10 at 633 nm |
| Surface quality | 60-40 (standard), 20-10 (precision) |
| Coating | Uncoated (TIR, solid glass) or metallic/dielectric-coated back surfaces (hollow retroreflectors) |
How It Works
Each of the three internal faces reflects the beam once. Bounce off three mutually perpendicular surfaces in sequence, and simple geometry guarantees the outgoing beam is parallel to the incoming one — offset, but not tilted. It's the same trick that lets a bicycle reflector bounce a car's headlights straight back at the driver, just built to much tighter tolerances.
Solid vs. Hollow
Solid glass corner cubes rely on TIR and need no coating, but they add optical path length through glass, which can distort a very precisely collimated beam. Hollow retroreflectors — three mirror-coated surfaces around an air gap — avoid that distortion and handle higher laser power, at a higher price.
Applications
- Laser alignment and tracking systems
- Distance and ranging measurement
- Retroreflective targets for interferometers
Buying Tips
Beam deviation accuracy is the spec that matters most for alignment and ranging work — check the retroreflector's specified deviation tolerance against what your system actually needs, since tighter tolerances cost significantly more.
